Apparatus for detecting broken threads or other disturbances in a fibre web

ABSTRACT

An apparatus for the supervision of fibrous webs, or other sheet-like material, particularly within the textile and paper industries, with the purpose of detecting faults in webs. An emitter is positioned at one side of the web and arranged to give off a beam of light essentially at right angles to the web extension. A receiver, positioned at the opposite side of the web, receives the beam of light. In accordance with the invention, the beam is imparted a particular movement covering an area of the web where faults are likely to arise and the immediate vicinity of said area. Evaluation means register any disturbances and compare them with a predetermined value, and upon excess of said predetermined value an impulse is emitted to a warning and/or stopping mechanism.

United States Patent [191 Lind et a1.

[ APPARATUS FOR DETECTING BROKEN THREADS OR OTHER DISTURBANCES IN AFIBRE WEB [75] Inventors: Bjorn Ivar Lind, Goteborg; Mans Gunnar OveMansson, Killeberg, both of Sweden [73] Assignee: Nordiska MaskinfiltAktiebolaget,

I-Ialmstad, Sweden [22] Filed: Aug. 17, 1972 [21] Appl. No.: 281,424

[30] Foreign Application Priority Data Aug. 23, 1971 Sweden 10637/71[52] U.S. C1 250/561, 28/51, 139/353 [51] Int. Cl. G0ln 21/30 [58] Fieldof Search... 250/219 S, 219 NE, 219 DF;

[56] References Cited UNITED STATES PATENTS 3,124,289 3/1964 Lynch 28/513,345,812 10/1967 Pickering 3,401,267 9/1968 Engle 3,447,213 6/1969 Dost28/51 3,536,926 10/1970 Friedrich 250/219 S 3,543,360 12/1970 Fertig28/51 June 18, 1974 3,677,307 7/1972 Fiorucci 139/353 3,717,771 2/1973Abilock 250/219 DF FOREIGN PATENTS OR APPLICATIONS 691,069 5/1953 GreatBritain Primary Examiner-James W. Lawrence Assistant ExaminerD. C. NelmsAttorney, Agent, or Firm-Kane, Dalsimer, Kane, Sullivan, Kurucz &Goldstein ABSTRACT An apparatus for the supervision of fibrous webs, orother sheet-like material, particularly within the textile and paperindustries, with the purpose of detecting faults in webs. An emitter ispositioned at one side of the web and arranged to give off a beam oflight essentially at right angles to the web extension. A receiver,positioned at the opposite side of the web, receives the beam of light.In accordance with the invention, the beam is imparted a particularmovement covering an area of the web where faults are likely to ariseand the immediate vicinity of said area. Evaluation means register anydisturbances and compare them with a predetermined value, and uponexcess of said predetermined value an impulse is emitted to a warningand/or stopping mechanism.

12 Claims, 3 Drawing Figures PATENIEU JUN 1 8 m:

SHEU 1 BF 2 PATENTEDJUNIBIW 3.818.236

SHEET 2 OF 2 l; 2O CLOCK 21 I9\ 2/ COUNTING DE VICE LEVEL SENSOR 22 I8 TCOMPARATOR FILTER SWITCH CONTROL AMPLIFIER 24 ALARIVI SIGNAL RECEIVER--Q 25 MOTOR APPARATUS FOR DETECTING BROKEN THREADS OR OTHER DISANCES IN AFIBRE WEB BACKGROUND OF THE INVENTION In order to avoid as much aspossible weaving faults caused by breakage of one or several warpthreads during weaving, it is necessary to supervise the threadscontinuously throughout the weaving procedure. Since each individualweaver handles a large number of weaves, manual supervision of thecondition of the warp threads naturally is completely insufficient to detect defects of this kind to effect stoppage of the machine before longstretches of faulty material webs have already been woven.

To solve this problem automated supervision or inspection systems havebeen developed, these systems comprising an emitter giving off a beam oflight at an angle essentially normal to the warp threads, which beam oflight is received by a receiver positioned at the opposite side of theweave and arranged to measure the change of intensity of the beam oflight occurring when the the light beam path is disturbed or interruptedby a warp thread. Means are connected to said receiver to emit, at apredetermined disturbance, an impulse providing an alarm signal and/orstopping the weaving.

In these known systems both the emitter and the receiver are fixed tothe reed in such a way that the emitter gives off a beam of light whichin response to the movement of the reed describes an arcuate motion pathlying completely within the shed, i.e., between the warp threads of theupper and the lower part of the warp. When a break occurs of a thread ofthe upper part of the warp, this broken thread will hang down within theshed and thus interrupt the beam of light when the latter travels to thereceiver. This disturbance, caused by the pendant thread, will cause adecrease of intensity of the light reaching the receiver, this intensitydecrease causing the means connected to the receiver to startfunctioning and thus stop the weaving. If, on the other hand, a threadof the lower part of the warp breaks, this thread will hang down belowthe area scanned by the beam and the weaving operation will continue,resulting in a deficient product.

Mounting of the supervisory components directly on the reed has theeffect that the maximum number of scanning movements that may beperformed is two for each working stroke of the reed. In addition, bothemitter and receiver will be exposed to strong vibrations andconsiderable stress on account of the heavy acceleration movements ofthe reed and its thrust-like deceleration movements.

The emitter of these earlier systems operates with a beam of light whichoriginally has a diameter of between 2 and 3 centimeters and whichdiverges to a diameter of up to between 5 and 6 centimeters, dependenton the width of the weave. In the receiver, only a smaller amount ofthis light is used for detecting purposes and the result is thatdisturbances occur as shadows in the receiver. However, following thelaws of optics, the shadowing caused by a broken thread positionedadjacent the emitter is much less than that caused by a broken threadhaving the same dimensions but positioned close to the receiver, and asa result great variations of shadowing will arise for the same degree ofdisturbance at different areas of the warp. This is clearlyunsatisfactory as the receiver then must be made particularly sensitivein order to be able to register thread breakages at the emitter side ofthe warp, and this hightened sensitivity has the effect that alsosmaller particles, such as grains of dust passing the beam of the lightat the receiver side will release an impulse to stop the apparatus.

In case of failure of the receiver of these earlier systems for onereason or another, the weaving furthermore will continue also at theoccurrence of thread breaks which normally would bring about stoppage.

SUMMARY OF THE INVENTION In order to provide for supervision of web inan effi cient manner, an apparatus is suggested in accordance with thepresent invention which is essentially characterised in that theemitter, which is positioned at one side of the web, is arranged to giveoff an essentially coherent light beam to which means impart such amovement that the light beam travels within an area of the web wheredisturbances are likely to arise, and in that the means connected to thereceiver are arranged both to register the number of disturbances pertime unit, to compare the number of registered disturbances per timeunit with a predetermined value, and also, in case of deviation of theregistered value from the predetermined value, to emit said impulse.

This apparatus thus provides supervision while making use of the emittedlight fully for the scanning activity which embraces all warp threads.As a result is obtained in the receiver a decrease of intensity which isproportional to the dimension of the disturbing object, irrespective ofthe distance between the receiver and the disturbing object. Inaddition, the apparatus does not suffer from any one of thedisadvantages mentioned previously.

BRIEF DESCRIPTION OF THE DRAWINGS The structure and function of theapparatus will be described more in detail in the following withreference to the accompanying drawings, wherein FIG. 1 illustrates in ahighly schematic view from above the apparatus as applied to a weavingloom,

FIG. 2 is a side view of the loom of FIG. 1, and

FIG. 3 is a diagrammatic basic circuit diagramme showing the underlyingprinciple of the receiver part of the apparatus.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT The loom illustrated inFIGS. 1 and 2 comprises generally a warp beam 1 on which warp threads 2are wound. Only a small number of these threads 2 is shown in FIG. 1.The warp threads 2 pass through healds 3 where, with the aid of shafts,they form an aperture 4 the shed through which weft threads are insertedand compacted with 'the aid of a weave reed 5, the latter having beenexcluded from FIG. 1 in order not to clutter the drawing and being shownonly in FIG. 2. The fabric web 6 formed during weaving is thereafterwound onto a fabric beam 7.

At the level of the shed 4, an emitter 8 is arranged at one longitudinalside of the loom, said emitter giving off an essentially coherent beamof light 9 and being mounted essentially immovably relative to themachine frame of the loom, either by being attached directly on theframe or in order to avoid machine vibrations on the machine base. Atthe opposite side of the shed, a receiver it) is positioned in a similarmanner, said receiver being provided with a collecting input screencorresponding to the path of movement of the light, and preferablycomprising a photoelectric cell arranged to measure the intensity of theincoming beam of light.

Adjacent the emitter 8 there is a device 11 which is arranged to imparta definite movement to the beam of light 9 from the emitter. The device11 comprises in accordance with the illustrated, preferred embodiment ahollow shaft 12 which is orientated in alignment with the direction ofissue of the beam of light 9 in such a manner that the beam of lightpasses through the shaft. At the shaft end remote from the emitter theshaft is provided with a nonrotational optical element 13 which mayconsist of mirrors, lenses or prisms and is arranged to effect aparallel movement of the beam of light over a short distance. The shaft12 is rotatably mounted and driven at a high speed by a motor 14,whereby the beam of light 9 is imparted a rapid rotational movement in aplane perpendicular to the warp threads 2.

Below the lower part of the warp catcher means 15 are provided, thesemeans extending essentially normally to the extension of the warpthreads and consisting in their most simple version of wires suspendedbeneath the shed in a manner permitting a thread of the lower warp, whenbreaking, to remain in a pending position within the area being scannedby the moving beam of light 9 whereas the wires themselves areorientated in a way preventing them from interfering with orinterrupting the rotational path of the beam of light at any point.

FIG. 2 illustrates in a more detailed manner the position of the catchermeans 15 as also the extent of the path of movement 16 along which thebeam of light 9 carries out its scanning action. This Figure also showsthe position of the reed 5 whereas the detecting apparatus is notillustrated here in order to give a clearer view of the scanned path 16.

FIG. 3 is a basic circuit diagramme showing the underlying principle ofthe construction of the receiver portion of the apparatus.

To the receiver it) proper is coupled an amplifier 17 which amplifiesthe input pulses. Thereafter is connected a filter 18 which forwardspulses having a determined frequency to a level-sensing unit 19. Thelatter is adjustable such that pulses exceeding a predetermined valueare permitted passage to a clock 20 determining the measuring intervaland providing the measuring time to a counting device 21 counting thenumber of pulses per time unit. This number is compared in a comparator22 to a predetermined value which is dependent on the speed at which theshaft 12 is rotated and on the measuring time. Upon occurrence ofdeviations of the measured value from the predetermined one, thecomparator 22 emits an impulse to a means 23 arranged to control aswitch 24 in the supply line to the loom drive motor 25. The switch 24is preferably arranged to close a circuit for an alarm signal apparatus26 in connection with breaking the circuit of the drive motor 25.

As long as the weaving continues without faults the beam of light 9will, in accordance with the shown embodiment, be exposed to disturbanceby warp threads 2 four times for each rotational revolution. Eachsequence of measuring thus comprises a large number of revolutions andthe number is determined by the clock 20 in addition to which eachmeasuring sequence lasts a comparatively short time in relation to theduration of the loom working stroke, i.e., the reciprocating movement ofthe reed. The photo-electric cell of the receiver then receives a numberof signals corresponding to the number of revolutions multiplied byfour. Analogy is thus obtained in the comparator 22 between thepredetermined value and the one registered by the counter. In thissituation, the comparator does not issue an impulse to the breakingmeans 23.

Upon occurrence of a warp thread break, irrespective of whether thebreak occurs in the upper or lower part of the warp, the light beam willbe disturbed or interrupted one time in excess of the four normal timesper revolution. This creates a discrepancy between the predeterminedvalue and the registered value and the comparator will find that analogyis missing and thus emit an impuise to stop the motor 25. Since eachmeasuring sequence has a duration which is brief in comparison with thereed working stroke, any break of a warp thread will very rapidly havethe effect of stopping the weaving machine, and in case an alarm signaldevice 26 is incorporated in the receiver, stopping of the machine willlikewise be detected very quickly.

In case any one of the details in the receiver portion up to thecomparator and including the receiver proper should fail and stopfunctioning in the intended manner, the comparator will likewise bringabout stopping. The probability that too low a disturbance impulse valuecaused by apparatus failure could be evened out by one or several threadbreaks occurring simultaneously is negligible.

The movement which the coherent light beam 9 is imparted has beendescribed in the aforegoing as a rotating movement. This motion patternis comparatively easy to achieve but what is essential to thefunctioning of the detecting apparatus is that the light beam 9 moves insuch a way that the shed, the upper warp and the lower warp and the areaclosest to the lower warp are scanned, and for this reason it is alsopossible to use a very simple movement such as a rectilinear one.

The clock 20 is programmed to release measuring sequences atpredetermined intervals and to prevent starting of measure sequencesduring exchange of the reeds.

The coherent beam of light 9 given off by the emitter 8 preferably is oflaser type although it is also possible to use other kinds of light.

The emitter described above gives off a beam of light which isessentially normal to the threads to be supervised. This does not,however, necessarily mean that the emitter must be positioned at rightangles to the warp but the beam of light may be forwarded to its pointof departure via so called fibre optics. The same technique may also beused to supervise several points with the aid of the very same emitter.The clock 20 which decides the measuring intervals may also have theform of several clocks which connect and disconnect their individualcounter for the registration of the situation at the various portions ofthe area within which the light beam moves. This makes possible emittance of several kinds of impulses for disturbances occurring withindifferent portions of the area of move ment of the light beam.

The apparatus in accordance with the invention has been described inconnection with use in a particular application but the possibilities ofmodifications are numerous within the scope of the appended claims.

The invention thus is not limited to use in connection with looms todetect broken warp threads. Within the textile industry there arenumerous processes where webs of threads or filaments run in one and thesame plane. As examples may be mentioned spinning and twisting machines,winding machines, warping machines and knitting machines. Also withinthe paper industry the invention may find applications such as forinstance to scan or continuously supervise the paper web of a papermachine. On the whole, the apparatus in accordance with the inventionmay be used to scan any regular systems for detecting and registeringdisturbances.

What we claim is:

1. An improved apparatus for detecting disturbances of a fibrous web,such as broken threads, comprising an emitter giving off a beam of lightdirected essentially at right angles to the threads, a receiverpositioned at the opposite side of the threads and arranged to measure achange of intensity to which said beam of light is subjected when thepath of said beam of light is interrupted, e.g., by a thread, meansconnected to said receiver for emitting, in response to a predetermineddisturbance, an impulse capable of providing circuit response, theimprovement comprising the emitter giving off an essentially coherentbeam of light, a device provided to impart to said beam of light amovement of travel within an area where disturbances are expected tooccur, said means connected to said receiver including counting means tocount the number of disturbances per time unit and comparatory means tocompare said number of disturbances per time unit with a predeterminednumber, and to emit said impulse in case of any discrepancy between saidnumber of disturbances per time unit and said predetermined number.

2. The improved apparatus as claimed in claim 1 utilized for detectionof broken upper and lower warp 3. The improved apparatus as claimed inclaim 1, wherein a predetermined number of scanning operations of saidarea defines a measuring sequence.

4. The improved apparatus as claimed in claim 3, wherein said beammovement imparting device is arranged to give to said beam of light aparticular movement a plurality of times per measuring sequence.

5. The improved apparatus as claimed in claim 1, wherein said beammovement imparting device consists of a hollow shaft, being rotated,through which hollow shaft passes said beam of light from the emitter,an optical element being provided on said shaft to give said beam oflight a back and forth movement of adjustable width.

6. The improved apparatus as claimed in claim 1, wherein said beam oflight emitted by said emitter is a laser beam.

7. The improved apparatus as claimed in claim 1, wherein both saidemitter and said receiver are mounted rigidly relative to each other.

8. The improved apparatus as claimed in claim 1, comprising catchermeans positioned beneath the threads to prevent broken threads fromhanging down, this arrangement retaining said threads within said areabeing scanned by said beam of light without causing any disturbance tosaid beam of light by said catcher means themselves.

9. The improved apparatus as claimed in claim 1, comprising clock meansconnected between said receiver and said counting means and programmedto connect and disconnect said counting means.

10. The improved apparatus as claimed in claim 1, comprising breakingmeans, switch means connected between said receiver and said breakingmeans and programmed to carry out measurings at predetermined occasions.

11. The improved apparatus as claimed in claim 10, comprising means tointerrupt measurings upon shift of weaving harness.

12. The improved apparatus as claimed in claim 1, comprising a unitcoupled between the receiver and said counting means to emit an impulseto said counting means only upon change of intensity exceeding apredetermined value.

1. An improved apparatus for detecting disturbances of a fibrous web,such as broken threads, comprising an emitter giving off a beam of lightdirected essentially at right angles to the threads, a receiverpositioned at thE opposite side of the threads and arranged to measure achange of intensity to which said beam of light is subjected when thepath of said beam of light is interrupted, e.g., by a thread, meansconnected to said receiver for emitting, in response to a predetermineddisturbance, an impulse capable of providing circuit response, theimprovement comprising the emitter giving off an essentially coherentbeam of light, a device provided to impart to said beam of light amovement of travel within an area where disturbances are expected tooccur, said means connected to said receiver including counting means tocount the number of disturbances per time unit and comparatory means tocompare said number of disturbances per time unit with a predeterminednumber, and to emit said impulse in case of any discrepancy between saidnumber of disturbances per time unit and said predetermined number. 2.The improved apparatus as claimed in claim 1 utilized for detection ofbroken upper and lower warp threads in weaving, wherein said movementimparted to said beam of light by said device is effected within an arealying between the upper and the lower warp threads and above and beneaththese threads.
 3. The improved apparatus as claimed in claim 1, whereina predetermined number of scanning operations of said area defines ameasuring sequence.
 4. The improved apparatus as claimed in claim 3,wherein said beam movement imparting device is arranged to give to saidbeam of light a particular movement a plurality of times per measuringsequence.
 5. The improved apparatus as claimed in claim 1, wherein saidbeam movement imparting device consists of a hollow shaft, beingrotated, through which hollow shaft passes said beam of light from theemitter, an optical element being provided on said shaft to give saidbeam of light a back and forth movement of adjustable width.
 6. Theimproved apparatus as claimed in claim 1, wherein said beam of lightemitted by said emitter is a laser beam.
 7. The improved apparatus asclaimed in claim 1, wherein both said emitter and said receiver aremounted rigidly relative to each other.
 8. The improved apparatus asclaimed in claim 1, comprising catcher means positioned beneath thethreads to prevent broken threads from hanging down, this arrangementretaining said threads within said area being scanned by said beam oflight without causing any disturbance to said beam of light by saidcatcher means themselves.
 9. The improved apparatus as claimed in claim1, comprising clock means connected between said receiver and saidcounting means and programmed to connect and disconnect said countingmeans.
 10. The improved apparatus as claimed in claim 1, comprisingbreaking means, switch means connected between said receiver and saidbreaking means and programmed to carry out measurings at predeterminedoccasions.
 11. The improved apparatus as claimed in claim 10, comprisingmeans to interrupt measurings upon shift of weaving harness.
 12. Theimproved apparatus as claimed in claim 1, comprising a unit coupledbetween the receiver and said counting means to emit an impulse to saidcounting means only upon change of intensity exceeding a predeterminedvalue.